On Thu, 26 Jun 2014 16:33:38 -0400 Vivek Goyal <vgoyal at redhat.com> wrote:
> Previous patch provided the interface definition and this patch prvides
> implementation of new syscall.
>
> Previously segment list was prepared in user space. Now user space just
> passes kernel fd, initrd fd and command line and kernel will create a
> segment list internally.
>
> This patch contains generic part of the code. Actual segment preparation
> and loading is done by arch and image specific loader. Which comes in
> next patch.
>
> ...
>
> --- a/kernel/kexec.c
> +++ b/kernel/kexec.c
> @@ -6,6 +6,8 @@
> * Version 2. See the file COPYING for more details.
> */
>
> +#define pr_fmt(fmt) "kexec: " fmt
> +
> #include <linux/capability.h>
> #include <linux/mm.h>
> #include <linux/file.h>
> @@ -326,6 +328,215 @@ out_free_image:
> return ret;
> }
>
> +static int copy_file_from_fd(int fd, void **buf, unsigned long *buf_len)
> +{
> + struct fd f = fdget(fd);
> + int ret = 0;
unneeded initialisation.
> + struct kstat stat;
> + loff_t pos;
> + ssize_t bytes = 0;
> +
> + if (!f.file)
> + return -EBADF;
> +
> + ret = vfs_getattr(&f.file->f_path, &stat);
> + if (ret)
> + goto out;
> +
> + if (stat.size > INT_MAX) {
> + ret = -EFBIG;
> + goto out;
> + }
> +
> + /* Don't hand 0 to vmalloc, it whines. */
> + if (stat.size == 0) {
> + ret = -EINVAL;
> + goto out;
> + }
> +
> + *buf = vmalloc(stat.size);
> + if (!*buf) {
> + ret = -ENOMEM;
> + goto out;
> + }
> +
> + pos = 0;
> + while (pos < stat.size) {
> + bytes = kernel_read(f.file, pos, (char *)(*buf) + pos,
> + stat.size - pos);
> + if (bytes < 0) {
> + vfree(*buf);
> + ret = bytes;
> + goto out;
> + }
> +
> + if (bytes == 0)
> + break;
Here we can get a short read: (pos < stat.size). Seems to me that it
is risky to return this result to the caller as if all is well.
> + pos += bytes;
> + }
> +
> + *buf_len = pos;
> +out:
> + fdput(f);
> + return ret;
> +}
>
> ...
>
